<?php
declare(strict_types=1);

function fail_json(int $status, string $message): never {
    http_response_code($status);
    header('Content-Type: application/json; charset=utf-8');
    header('Cache-Control: no-store');
    echo json_encode(['error' => $message, 'serverTime' => (int) round(microtime(true) * 1000)], JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
    exit;
}

function write_all($socket, string $value): void {
    $written = 0;
    $length = strlen($value);
    while ($written < $length) {
        $result = fwrite($socket, substr($value, $written, 64 * 1024));
        if ($result === false || $result === 0) {
            fclose($socket);
            fail_json(502, 'Failed to send the request to the LinkField server.');
        }
        $written += $result;
    }
}

function request_body(int $maximum): array {
    $input = fopen('php://input', 'rb');
    if (!is_resource($input)) fail_json(400, 'Could not read the request body.');
    $declared = trim((string) ($_SERVER['CONTENT_LENGTH'] ?? ''));
    if ($declared !== '') {
        if (!preg_match('/^[0-9]+$/D', $declared)) { fclose($input); fail_json(400, 'Invalid request content length.'); }
        $length = (int) $declared;
        if ($length > $maximum) { fclose($input); fail_json(413, 'Request body is too large.'); }
        return [$input, $length];
    }
    $temporary = fopen('php://temp/maxmemory:1048576', 'w+b');
    if (!is_resource($temporary)) { fclose($input); fail_json(500, 'Could not stage the request body.'); }
    $length = 0;
    while (!feof($input)) {
        $chunk = fread($input, 64 * 1024);
        if ($chunk === false) { fclose($input); fclose($temporary); fail_json(400, 'Could not read the request body.'); }
        $length += strlen($chunk);
        if ($length > $maximum) { fclose($input); fclose($temporary); fail_json(413, 'Request body is too large.'); }
        if ($chunk !== '' && fwrite($temporary, $chunk) !== strlen($chunk)) { fclose($input); fclose($temporary); fail_json(500, 'Could not stage the request body.'); }
    }
    fclose($input);
    rewind($temporary);
    return [$temporary, $length];
}

function write_body($socket, $body, int $length): void {
    $written = 0;
    while ($written < $length) {
        $chunk = fread($body, min(64 * 1024, $length - $written));
        if ($chunk === false || $chunk === '') { fclose($body); fclose($socket); fail_json(400, 'Request body ended before its declared length.'); }
        write_all($socket, $chunk);
        $written += strlen($chunk);
    }
    fclose($body);
}

$portFile = __DIR__ . DIRECTORY_SEPARATOR . '.linkfield-port';
if (!is_file($portFile)) {
    fail_json(503, 'LinkField server is not running. Run npm start in this directory.');
}
$portText = trim((string) @file_get_contents($portFile));
$port = filter_var($portText, FILTER_VALIDATE_INT, ['options' => ['min_range' => 1, 'max_range' => 65535]]);
if ($port === false) {
    fail_json(503, 'LinkField server port information is invalid. Restart npm start.');
}

$targetPath = isset($_GET['path']) ? (string) $_GET['path'] : '';
if (!preg_match('#^/api/(?:cloud|player|realtime)(?:/[A-Za-z0-9_-]+)*$#D', $targetPath)) {
    fail_json(400, 'Invalid LinkField API path.');
}
$query = $_GET;
unset($query['path']);
if ($query) {
    $targetPath .= '?' . http_build_query($query, '', '&', PHP_QUERY_RFC3986);
}

$method = strtoupper((string) ($_SERVER['REQUEST_METHOD'] ?? 'GET'));
if (!in_array($method, ['GET', 'POST', 'HEAD'], true)) {
    fail_json(405, 'Method not allowed.');
}
[$body, $bodyLength] = request_body(8 * 1024 * 1024);

$authorization = '';
if (function_exists('getallheaders')) {
    $headers = getallheaders();
    if (is_array($headers)) {
        foreach ($headers as $name => $value) {
            if (strcasecmp((string) $name, 'Authorization') === 0) $authorization = (string) $value;
            if (strcasecmp((string) $name, 'X-LinkField-Authorization') === 0 && $authorization === '') $authorization = (string) $value;
        }
    }
}
if ($authorization === '') {
    $authorization = (string) ($_SERVER['HTTP_AUTHORIZATION'] ?? $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ?? $_SERVER['HTTP_X_LINKFIELD_AUTHORIZATION'] ?? '');
}

$socket = @stream_socket_client(
    'tcp://127.0.0.1:' . $port,
    $errorNumber,
    $errorMessage,
    3,
    STREAM_CLIENT_CONNECT
);
if (!is_resource($socket)) {
    fail_json(502, 'LinkField server is not reachable on its local port. Restart npm start.');
}
stream_set_timeout($socket, 30);

$requestHeaders = [
    $method . ' ' . $targetPath . " HTTP/1.1",
    'Host: 127.0.0.1:' . $port,
    'Connection: close',
    'Accept: application/json',
    'Content-Type: application/json',
    'Content-Length: ' . $bodyLength,
];
if ($authorization !== '') $requestHeaders[] = 'Authorization: ' . str_replace(["\r", "\n"], '', $authorization);
$remoteAddress = (string) ($_SERVER['REMOTE_ADDR'] ?? '');
if (preg_match('/^[0-9A-Fa-f:.]{3,64}$/', $remoteAddress)) $requestHeaders[] = 'X-Forwarded-For: ' . $remoteAddress;
write_all($socket, implode("\r\n", $requestHeaders) . "\r\n\r\n");
write_body($socket, $body, $bodyLength);

$response = '';
$separator = false;
while (!feof($socket) && $separator === false && strlen($response) <= 64 * 1024) {
    $chunk = fread($socket, 8192);
    if ($chunk === false) break;
    $response .= $chunk;
    $separator = strpos($response, "\r\n\r\n");
}
$meta = stream_get_meta_data($socket);
if ($response === '' || $separator === false || !empty($meta['timed_out'])) {
    fclose($socket);
    fail_json(504, 'LinkField server did not respond in time.');
}
$headerText = substr($response, 0, $separator);
$responseBody = substr($response, $separator + 4);
$headerLines = explode("\r\n", $headerText);
$statusLine = array_shift($headerLines);
if (!preg_match('#^HTTP/\d(?:\.\d)?\s+(\d{3})#', (string) $statusLine, $statusMatch)) {
    fail_json(502, 'Invalid status from the LinkField server.');
}
http_response_code((int) $statusMatch[1]);
foreach ($headerLines as $line) {
    $colon = strpos($line, ':');
    if ($colon === false) continue;
    $name = trim(substr($line, 0, $colon));
    $value = trim(substr($line, $colon + 1));
    if (in_array(strtolower($name), ['content-type', 'cache-control', 'x-content-type-options', 'retry-after'], true)) {
        header($name . ': ' . $value, true);
    }
}
header('X-LinkField-Bridge: php', true);
header_remove('X-Powered-By');
if ($method !== 'HEAD') {
    echo $responseBody;
    while (!feof($socket)) {
        $chunk = fread($socket, 64 * 1024);
        if ($chunk === false) break;
        echo $chunk;
        if (function_exists('flush')) flush();
    }
}
fclose($socket);